1. Field of the Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to an active matrix substrate having an electrostatic discharge (ESD) protection circuit.
2. Description of the Related Art
The electrostatic discharge phenomenon is found almost everywhere. Due to electronic affinity or repulsion between different types of objects, the process of separating of two objects after bringing into contact with each other easily leads to a charge transfer between the objects. Once an amount of electric charges has been accumulated to produce a charged object, an instant charge transfer to a second object having a different potential occurs when the charged body is in contact with or is brought near the second object. This is the so-called “electrostatic discharge” (ESD).
In general, the probability of receiving damage from electrostatic discharge through the manufacturing, assembly, and transportation processes or even in normal use by the consumer is relatively high. Therefore, it is important for an electronic product to have a design for protection against electrostatic discharge so that the product has a longer life span. In particular, the damage due to an electrostatic discharge in a product fabricated using advanced semiconductor production technologies such as integrated circuit (IC) or flat panel display can be easily prone. This is because the components inside the semiconductor product have very small dimensions so that the damaging effect caused by a transient high voltage ESD on the circuits inside the integrated circuit or flat panel display is permanent. Ultimately, the device simply malfunctions and is scrapped.
For the existing flat panel display, an electrostatic discharge often leads to the production of dot defects or line defects on the display panel. Because of difficulties in the absolute prevention of electrostatic discharge during the process of fabricating a flat panel display, the conventional technique often relies on an electrostatic discharge (ESD) protection circuit inside the flat panel display to minimize the damages inflicted upon the display due to possible ESD. At the present, the most common ESD protection circuit used inside the flat panel display includes an inner short ring (ISR) and an outer short ring (OSR). However, the combination of the inner short ring and the outer short ring could hardly protect the first data line or the ones close to the first data line and the last data line or the ones close to the last data line if the discharge voltage is excessively high. Therefore, the ones close to the first or the ones close to the last data lines are more vulnerable to damages caused by an ESD, and consequently these lines have more line defects.